(1)45+55÷5-20,
=45+11-20,
=56-20,
=36;
(2)12×(280-80÷4),
=12×(280-20),
=12×260,
=780;
故答案为:
错误,
45+55÷5-20,
=45+11-20,
=56-20,
=36;
错误,
12×(280-80÷4),
=12×(280-20),
=12×260,
=780;
(1)45+55÷5-20,
=45+11-20,
=56-20,
=36;
(2)12×(280-80÷4),
=12×(280-20),
=12×260,
=780;
故答案为:
错误,
45+55÷5-20,
=45+11-20,
=56-20,
=36;
错误,
12×(280-80÷4),
=12×(280-20),
=12×260,
=780;